I started to write a response to Anton's comment to my previous post on the subject, and realized that it was almost as long as the blog entry itself. Really, I think that Anton is just being pedantic and playing Devil's Advocate, but he makes an important point: "Well, what is a company if not a collection of people? ... I am on LinkedIn = LogLogic on LinkedIn. I blog and a post goes to Facebook -> LogLogic message speads."
And that seems to be the entirety of the "strategy" being used by most security companies. Rather than using any sort of coordinated strategy around branding through the social media sites, it seems like most of the companies figure that their employees will "get the message across" by accident.
Not to pick on anyone, but I'll use an example I'm intimately friendly with (because I started the blog when I was there) - how is nCircle using those tools to market their blog? Simple answer: they're not. There's nobody pushing the use of LinkedIn Answers or Yahoo Answers, no twittering of blog posts, no use of Facebook or (though I hate it) MySpace to drive traffic and/or awareness of what they're doing. They might argue that it's not part of branding to their targets, but I'd disagree - I know a lot of people in their target audience that are on each of the social media entities above.
While I singled out nCircle, they at least have a blog, unlike most of the companies in our space.
For two good examples of "how it could be otherwise", check out the way that Jason Alba uses twitter entries to promote every blog entry he writes. Or the way that Stacy Thayer is using Facebook to market the SOURCE Conference. (Aside: have you bought your tickets yet? They're going really fast.